Contemporary computer systems offer users the ability to magnify a portion of their display screen, typically for providing visually-impaired users with better accessibility to computers, although also offering mainstream users the benefit of magnification in certain contexts. The portion of the display screen that is magnified can be selectively based on where the mouse is located, where the keyboard is focused, and/or where the user is otherwise editing, e.g., when selecting content such as for cutting and pasting.
In general, when the user runs a magnifier, a magnification window is opened and the magnified content displayed in that window. The user can adjust the magnification window in size and position, adjust the magnification level, and possibly choose other effects, e.g., color inversion. One such magnifier program operates by driver hooking, to intercept graphics calls sent towards the video driver, essentially in a screen capture operation, where the magnifier program then scales up a corresponding graphics image in the magnification window.
Because with any magnification factor greater than 1×, the magnified image is larger than the source image. As a result, it is often necessary for the user to navigate to locate a desired portion of the source region for magnification in the magnification window. When working with a large source region, it is fairly easy for users to lose their orientation with respect to the source image, that is, the user sees a magnified image in the magnification window but cannot determine what portion of the source is being magnified.